docs: def _create_callback(self, function, wrap_result):
      """Create MPD command related response callback.
      """
      if not isinstance(function, Callable):
          return None
      def command_callback():
          # command result callback expects response from MPD as iterable lines,
          # thus read available lines from socket
          res = function(self, self._read_lines())
          # wrap result in iterator helper if desired
          if wrap_result:
              res = self._wrap_iterator(res)
          return res
      return command_callback